Water is an expensive resource to store aboard passenger transport vehicles, such as aircraft, due to its high density and large volume of consumption on flights, especially international flights. For example, on-board a B777 sized aircraft tasked with a 10 hour mission, passenger use of potable water from sink faucets accounts for about 135 gallons of water pouring down lavatory sinks each flight, which accounts for about 40% of in-flight water consumption. This water is generally referred to as “grey water,” which refers to water that has been soiled but that does not contain sewage or “black water.” Grey water is the spent or used water that has been used for hand-washing, and may contain contaminants such as soaps or other detergents.
A method or system to recycle grey water would be of benefit to airlines in many capacities. For example, it would reduce the overall consumption of water; it would reduce the mass of the water required to be carried per flight, which could generate the ability to carry alternate payload instead of water; and it would allow the airline to tout itself as environmentally-friendly and as interested in conservation of resources. Modern technologies to produce potable water from grey water have not been designed for aircraft use; they tend to be heavy and large or treatment takes far too long for the 10 hour flight-time of even a long haul mission. The principles of municipal water treatment have been used to design a small scale treatment unit, sized for vehicle lavatories. Suspended solids, typically removed via gravity in large sedimentation pools, will be removed utilizing grey water filtration technology. The chemicals contributing to biochemical oxygen demand (BOD) will be removed quickly by a small scale biological trickling filter as opposed to the large scale degradation that occurs in municipal aeration tanks. Final clarification steps will be completed using further filtration and activated carbon, and a disinfection step utilizing UV will replace the large sedimentation and chlorine contact basins used to polish municipal water.
The present inventors have thus sought to develop a grey to potable water system with the potential to overcome these issues and to reduce the weight of each flight by significant amounts, while simultaneously cutting grey water waste.